Above ground pools are a less expensive alternative to the more expensive permanent in-ground pools. Newer above ground pools, which are being made of vinyl, or the older models based on aluminum walls clad in a vinyl liner are thin and a poor thermal insulator. In addition, the pool walls have a significant amount of surface area exposed to air, either directly via the pool's surface, or indirectly through the pool wall. As a result, these pools can be affected significantly by outdoor temperature swings which can prohibit a stable and desirable user temperature from being maintained. This problem is amplified throughout the pool season where cooler periods result in lowered pool temperatures that are undesirable to the user resulting in diminished use of the pool. As well, it is recognized that higher pool temperatures above a desired water temperature can also be undesirable.
The problem is not of being able to heat a pool from 0 C to (an example desired temperature of) 29 C, but to regulate the temperature about 29 C± several degrees throughout the pool season. As the natural ambient temperature is typically above (approximately) 22 C for most of the pool season, the pool will reach this temperature rapidly from the time that tap water (10-15 C) is added at the beginning of the pool season. It is also true that for most of the pool season, the desired/set target pool temperature is above the ambient outdoor temperature.
To summarize, above ground pool use is significantly affected by changing ambient temperatures which are different than the desired target temperature, leading to cooler or warmer undesirable pool temperatures, which result in diminished pool use. The challenge then is to auto-regulate the pool temperature about the desired target temperature ± several degrees throughout the pool season.
Also recognized is that energy efficiency is a desirable goal for the operation of pools (in-ground & above-ground), which are considered luxury items that can be energy intensive depending upon actual pool usage.
In order to overcome periods of cooler outdoor temperatures, which drive the pool temperature below the desired target temperature, several existing techniques can be employed to help raise the pool's temperature. One example is a pool heater that is controlled via sensing the actual water temperature, whereby a sensed water temperature below a set target temperature causes the pool heater to activate. Otherwise, the pool heater can be operated manually (i.e. switched on or off irrespective of the actual water temperature). However, use of a pool heater requires energy usage that many would deem to be an undesirable usage of energy resources.